mercurial/wireprotoserver.py

wireproto: define and use types for wire protocol commands

Wire protocol commands have historically been declared as
2-tuples in wireproto.commands. There are some additional features I'd
like to implement that require going beyond 2-tuples. But because
the 2-tuple API (both destructuring assignment and direct assignment
into the dict) is used throughout the code base and in 3rd party
extensions, we can't do a trivial type change.

This commit creates a new "commandentry" type to represent declared
wire protocol commands. It implements __getitem__ and __iter__ so
it can quack like a 2-tuple. The @wireprotocommand decorator now
creates "commandentry" instances.

We also create a "commanddict" type to represent the dictionary of
declared wire protocol commands. It inherits from "dict" but provides
a custom __setitem__ to coerce passed 2-tuples to "commandentry"
instances. wireproto.commands is now an instance of this type.

Various callers in core rely on the new functionality. And tests
pass. So I'm reasonably confident things will "just work" in 3rd
party extensions as well.

Differential Revision: https://phab.mercurial-scm.org/D1998

# Copyright 21 May 2005 - (c) 2005 Jake Edge <[e-mail]>
# Copyright 2005-2007 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import abc
import cgi
import struct
import sys

from .i18n import _
from . import (
    encoding,
    error,
    hook,
    pycompat,
    util,
    wireproto,
)

stringio = util.stringio

urlerr = util.urlerr
urlreq = util.urlreq

HTTP_OK = 200

HGTYPE = 'application/mercurial-0.1'
HGTYPE2 = 'application/mercurial-0.2'
HGERRTYPE = 'application/hg-error'

# Names of the SSH protocol implementations.
SSHV1 = 'ssh-v1'
# This is advertised over the wire. Incremental the counter at the end
# to reflect BC breakages.
SSHV2 = 'exp-ssh-v2-0001'

class abstractserverproto(object):
    """abstract class that summarizes the protocol API

    Used as reference and documentation.
    """

    __metaclass__ = abc.ABCMeta

    @abc.abstractproperty
    def name(self):
        """The name of the protocol implementation.

        Used for uniquely identifying the transport type.
        """

    @abc.abstractmethod
    def getargs(self, args):
        """return the value for arguments in <args>

        returns a list of values (same order as <args>)"""

    @abc.abstractmethod
    def getfile(self, fp):
        """write the whole content of a file into a file like object

        The file is in the form::

            (<chunk-size>\n<chunk>)+0\n

        chunk size is the ascii version of the int.
        """

    @abc.abstractmethod
    def redirect(self):
        """may setup interception for stdout and stderr

        See also the `restore` method."""

    # If the `redirect` function does install interception, the `restore`
    # function MUST be defined. If interception is not used, this function
    # MUST NOT be defined.
    #
    # left commented here on purpose
    #
    #def restore(self):
    #    """reinstall previous stdout and stderr and return intercepted stdout
    #    """
    #    raise NotImplementedError()

def decodevaluefromheaders(req, headerprefix):
    """Decode a long value from multiple HTTP request headers.

    Returns the value as a bytes, not a str.
    """
    chunks = []
    i = 1
    prefix = headerprefix.upper().replace(r'-', r'_')
    while True:
        v = req.env.get(r'HTTP_%s_%d' % (prefix, i))
        if v is None:
            break
        chunks.append(pycompat.bytesurl(v))
        i += 1

    return ''.join(chunks)

class webproto(abstractserverproto):
    def __init__(self, req, ui):
        self._req = req
        self._ui = ui

    @property
    def name(self):
        return 'http'

    def getargs(self, args):
        knownargs = self._args()
        data = {}
        keys = args.split()
        for k in keys:
            if k == '*':
                star = {}
                for key in knownargs.keys():
                    if key != 'cmd' and key not in keys:
                        star[key] = knownargs[key][0]
                data['*'] = star
            else:
                data[k] = knownargs[k][0]
        return [data[k] for k in keys]

    def _args(self):
        args = util.rapply(pycompat.bytesurl, self._req.form.copy())
        postlen = int(self._req.env.get(r'HTTP_X_HGARGS_POST', 0))
        if postlen:
            args.update(cgi.parse_qs(
                self._req.read(postlen), keep_blank_values=True))
            return args

        argvalue = decodevaluefromheaders(self._req, r'X-HgArg')
        args.update(cgi.parse_qs(argvalue, keep_blank_values=True))
        return args

    def getfile(self, fp):
        length = int(self._req.env[r'CONTENT_LENGTH'])
        # If httppostargs is used, we need to read Content-Length
        # minus the amount that was consumed by args.
        length -= int(self._req.env.get(r'HTTP_X_HGARGS_POST', 0))
        for s in util.filechunkiter(self._req, limit=length):
            fp.write(s)

    def redirect(self):
        self._oldio = self._ui.fout, self._ui.ferr
        self._ui.ferr = self._ui.fout = stringio()

    def restore(self):
        val = self._ui.fout.getvalue()
        self._ui.ferr, self._ui.fout = self._oldio
        return val

    def _client(self):
        return 'remote:%s:%s:%s' % (
            self._req.env.get('wsgi.url_scheme') or 'http',
            urlreq.quote(self._req.env.get('REMOTE_HOST', '')),
            urlreq.quote(self._req.env.get('REMOTE_USER', '')))

    def responsetype(self, prefer_uncompressed):
        """Determine the appropriate response type and compression settings.

        Returns a tuple of (mediatype, compengine, engineopts).
        """
        # Determine the response media type and compression engine based
        # on the request parameters.
        protocaps = decodevaluefromheaders(self._req, r'X-HgProto').split(' ')

        if '0.2' in protocaps:
            # All clients are expected to support uncompressed data.
            if prefer_uncompressed:
                return HGTYPE2, util._noopengine(), {}

            # Default as defined by wire protocol spec.
            compformats = ['zlib', 'none']
            for cap in protocaps:
                if cap.startswith('comp='):
                    compformats = cap[5:].split(',')
                    break

            # Now find an agreed upon compression format.
            for engine in wireproto.supportedcompengines(self._ui, self,
                                                         util.SERVERROLE):
                if engine.wireprotosupport().name in compformats:
                    opts = {}
                    level = self._ui.configint('server',
                                              '%slevel' % engine.name())
                    if level is not None:
                        opts['level'] = level

                    return HGTYPE2, engine, opts

            # No mutually supported compression format. Fall back to the
            # legacy protocol.

        # Don't allow untrusted settings because disabling compression or
        # setting a very high compression level could lead to flooding
        # the server's network or CPU.
        opts = {'level': self._ui.configint('server', 'zliblevel')}
        return HGTYPE, util.compengines['zlib'], opts

def iscmd(cmd):
    return cmd in wireproto.commands

def callhttp(repo, req, cmd):
    proto = webproto(req, repo.ui)

    def genversion2(gen, engine, engineopts):
        # application/mercurial-0.2 always sends a payload header
        # identifying the compression engine.
        name = engine.wireprotosupport().name
        assert 0 < len(name) < 256
        yield struct.pack('B', len(name))
        yield name

        for chunk in gen:
            yield chunk

    rsp = wireproto.dispatch(repo, proto, cmd)
    if isinstance(rsp, bytes):
        req.respond(HTTP_OK, HGTYPE, body=rsp)
        return []
    elif isinstance(rsp, wireproto.streamres_legacy):
        gen = rsp.gen
        req.respond(HTTP_OK, HGTYPE)
        return gen
    elif isinstance(rsp, wireproto.streamres):
        gen = rsp.gen

        # This code for compression should not be streamres specific. It
        # is here because we only compress streamres at the moment.
        mediatype, engine, engineopts = proto.responsetype(
            rsp.prefer_uncompressed)
        gen = engine.compressstream(gen, engineopts)

        if mediatype == HGTYPE2:
            gen = genversion2(gen, engine, engineopts)

        req.respond(HTTP_OK, mediatype)
        return gen
    elif isinstance(rsp, wireproto.pushres):
        val = proto.restore()
        rsp = '%d\n%s' % (rsp.res, val)
        req.respond(HTTP_OK, HGTYPE, body=rsp)
        return []
    elif isinstance(rsp, wireproto.pusherr):
        # drain the incoming bundle
        req.drain()
        proto.restore()
        rsp = '0\n%s\n' % rsp.res
        req.respond(HTTP_OK, HGTYPE, body=rsp)
        return []
    elif isinstance(rsp, wireproto.ooberror):
        rsp = rsp.message
        req.respond(HTTP_OK, HGERRTYPE, body=rsp)
        return []
    raise error.ProgrammingError('hgweb.protocol internal failure', rsp)

class sshserver(abstractserverproto):
    def __init__(self, ui, repo):
        self._ui = ui
        self._repo = repo
        self._fin = ui.fin
        self._fout = ui.fout

        hook.redirect(True)
        ui.fout = repo.ui.fout = ui.ferr

        # Prevent insertion/deletion of CRs
        util.setbinary(self._fin)
        util.setbinary(self._fout)

    @property
    def name(self):
        return 'ssh'

    def getargs(self, args):
        data = {}
        keys = args.split()
        for n in xrange(len(keys)):
            argline = self._fin.readline()[:-1]
            arg, l = argline.split()
            if arg not in keys:
                raise error.Abort(_("unexpected parameter %r") % arg)
            if arg == '*':
                star = {}
                for k in xrange(int(l)):
                    argline = self._fin.readline()[:-1]
                    arg, l = argline.split()
                    val = self._fin.read(int(l))
                    star[arg] = val
                data['*'] = star
            else:
                val = self._fin.read(int(l))
                data[arg] = val
        return [data[k] for k in keys]

    def getfile(self, fpout):
        self._sendresponse('')
        count = int(self._fin.readline())
        while count:
            fpout.write(self._fin.read(count))
            count = int(self._fin.readline())

    def redirect(self):
        pass

    def _sendresponse(self, v):
        self._fout.write("%d\n" % len(v))
        self._fout.write(v)
        self._fout.flush()

    def _sendstream(self, source):
        write = self._fout.write
        for chunk in source.gen:
            write(chunk)
        self._fout.flush()

    def _sendpushresponse(self, rsp):
        self._sendresponse('')
        self._sendresponse(str(rsp.res))

    def _sendpusherror(self, rsp):
        self._sendresponse(rsp.res)

    def _sendooberror(self, rsp):
        self._ui.ferr.write('%s\n-\n' % rsp.message)
        self._ui.ferr.flush()
        self._fout.write('\n')
        self._fout.flush()

    def serve_forever(self):
        while self.serve_one():
            pass
        sys.exit(0)

    _handlers = {
        str: _sendresponse,
        wireproto.streamres: _sendstream,
        wireproto.streamres_legacy: _sendstream,
        wireproto.pushres: _sendpushresponse,
        wireproto.pusherr: _sendpusherror,
        wireproto.ooberror: _sendooberror,
    }

    def serve_one(self):
        cmd = self._fin.readline()[:-1]
        if cmd and cmd in wireproto.commands:
            rsp = wireproto.dispatch(self._repo, self, cmd)
            self._handlers[rsp.__class__](self, rsp)
        elif cmd:
            self._sendresponse("")
        return cmd != ''

    def _client(self):
        client = encoding.environ.get('SSH_CLIENT', '').split(' ', 1)[0]
        return 'remote:ssh:' + client